The present disclosure relates to an image forming apparatus capable of forming a monochrome image in a single color and a color image composed of a plurality of colors.
An image forming apparatus such as a color printer includes, for example, a plurality of photosensitive drums that allow toner images for respective colors of black, yellow, magenta, and cyan to be formed thereon, and an intermediate transfer belt onto which the toner images formed on the plurality of photosensitive drums are to be transferred. The toner images for respective colors formed on the photosensitive drums are primarily transferred onto the intermediate transfer belt, and then collectively secondarily transferred onto a paper sheet from the intermediate transfer belt. Thus, a color image is formed on a paper sheet.
The above-described intermediate transfer belt extends over a drive roller linked with a drive source such as a motor, and a plurality of driven rollers. The intermediate transfer belt is rotated (endlessly moved) along with rotation of the drive roller, whereby toner images are sequentially transferred at positions opposing to the respective photosensitive drums.
The intermediate transfer belt may meander to deviate in the width direction of a roller during rotation. If the intermediate transfer belt meanders during rotation, when toner images are primarily transferred onto the intermediate transfer belt from the respective photosensitive drums, the positions of the toner images are displaced from each other, and this may cause color shift.
Conventionally, an image forming apparatus is known which includes a meandering resolving mode in which the orientation of a driven roller is set to a meandering resolving position so that the meandering intermediate transfer belt will return to a target position (reference position or such a range), and an equilibrium retaining mode in which the orientation of the driven roller is set to an equilibrium position so that the intermediate transfer belt will be retained at the target position. The image forming apparatus can return the meandering intermediate transfer belt to a target position by executing the meandering resolving mode.
The intermediate transfer belt may abnormally meander due to assembly defect of a drive mechanism such as a drive roller, for example. In the case where the intermediate transfer belt abnormally meanders, it may be impossible to return the intermediate transfer belt to a target position even if the image forming apparatus is operated in the above meandering resolving mode. In this case, printing by the image forming apparatus is automatically stopped. Then, until the defect is repaired, the image forming apparatus cannot perform either color printing and monochrome printing.